Linuron and Trifluralin are two weed-killers known in the literature. Their association permits control of a great number of infesting plants in agrarian cultures.
According to German patent application No. 2,037,265 the above-mentioned weed-killers can be simply mixed in a mixer before being used. Of course, they can be also individually spread on the soil.
This is inconvenient in practice, as it involves expensive treatments and handlings and can lead to errors of dosage.
Consequently, the procedure generally followed consists in spreading on the soil previously prepared compositions which, beside ensuring a correct dosage, do not require any particular treatments before being used.
As is known, the compositions most suitable for being spread on the soil are aqueous emulsions, which offer the advantage that they can be distributed uniformly by atomization and spraying by means of proper pumps, do not involve fatigue and are correctly vehicled to reach the infesting plants.
Unfortunately Linuron is insoluble in the common solvents which are not phytotoxic and often the emulsions prepared therefrom are not stable.
According to French patent application No. 2,239,941, Trifluralin and Linuron can be dissolved, in ratios of from 4:1 to 1:4, preferably from 2:1 to 1:2, in an alicyclic non-phytotoxic ketone, such as, for example, the cycloalkyl- or cycloalkenyl-ketones, in particular cyclohexanone or substituted cyclohexanones, in an amount sufficient to dissolve the weed-killers; the resulting solution can be then diluted with other solvents mixable with the alicyclic ketone; or furthermore, the mixture of weed-killers can be dissolved in a mix of an alicyclic ketone and a solvent mixable with said ketone, the latter being in an amount sufficient to dissolve the herbicides.
Aqueous emulsions can be prepared from such solutions already additioned with suitable anionic and non-ionic emulsifiers.
It is a common practice to sell the solutions as described hereinabove and to mix them with water at the time of use.
It has been observed that the aqueous emulsions prepared by using the compositions described in German patent application No. 2,037,265 at the concentrations employed for agricultural weed killing (from 0.375 to 1.5% in water) quickly deposit crystals of solid herbicides, which tend to settle on the bottom of the containers in which the emulsion is prepared, so subtracting active principle from the weed killer and often clogging the distributing pumps.